The inventive concept relates to photolithography. More particularly, the inventive concept relates to a method of measuring the distribution of energy in exposure light emitted by a scanner of photolithographic equipment.
Photolithography is a process used to transcribe a pattern, such as a circuit pattern or the like, onto a substrate. Photolithography includes an exposure process in which a layer of resist on a substrate is exposed to light directed through a reticle such that the resist is exposed to an image corresponding to that of a pattern of the reticle. The resist is then developed to remove the exposed portion thereof (in the case of a positive resist) or non-exposed portion thereof (in the case of a negative resist), thereby forming a resist pattern. Then, a layer of material lying under the resist pattern is etched using the resist pattern as a mask. As a result, a pattern corresponding to the pattern of the reticle is transcribed onto the substrate.
A scanner-type of exposure apparatus of a photolithography system employs an exposure slit through which the exposure light passes during exposure process, and a set-up in which the reticle and a stage supporting the substrate are moved relative to each other so that the resist is scanned by the exposure light. In general, both the dose and intensity of the energy of the exposure light passing through the slit must be uniform if the exposure process is to be carried out effectively.
Therefore, the dose and intensity of the exposure light must be controlled to be uniform during the exposure process. To this end, information regarding the exposure light or feedback is necessary. In this respect, it becomes necessary to accurately measure the “energy distribution” of the exposure light passing through the slit.
A sensor integrated with the scanner-type of exposure apparatus may be used to measure the energy distribution of the exposure light. Such a sensor, however, takes dozens of minutes to several hours to measure the energy distribution of light. The exposure system is not operated during this time. That is, there is a great deal of down time in an exposure process, performed by a scanner-type of exposure apparatus, in which the exposure light is controlled based on measurements obtained using a sensor.